I have fitted one of my X5s with a PX4Pilot Flight Controller and took it for its' first fly with this set-up this morning. Beautiful day, no wind, no clouds and not hot.
It all went perfectly. I tried Manual mode, Loiter Mode, Stability Mode and RTH Mode.
Happy enough with the results but need to slow it down a bit so I am making some adjustments to do so. It has a digital airspeed sensor so speed adjustments are fairly simple.
I need to work out how to brake my SimonK ESC to be happy.
Then, on to autonamous flights....